Control data transmission over a data channel by a controlling base station

ABSTRACT

A controlling base station sends, to a wireless communication device, control data related to communication between a communication base station and the wireless communication device. The control data is transmitted in accordance with a communication specification and is transmitted to allow reception by the wireless communication device of the control data within a data channel having a frequency and time allocated by the communication specification for the wireless communication device to receive data transmissions from the communication base station.

RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.12/782,479, entitled “CONTROL DATA TRANSMISSION OVER A DATA CHANNEL BY ACONTROLLING BASE STATION”, filed May 18, 2010, hereby expresslyincorporated by reference in its entirety, herein.

BACKGROUND

The invention relates in general to wireless communication systems andmore specifically to managing control signals in a wirelesscommunication system.

Base stations in cellular communication systems provide communicationsservices to wireless communication devices within geographical cellswhere each base station exchanges signals with wireless communicationdevices within an associated cell. The size and shape of each cell and,therefore, the coverage area of the base station are determined byseveral factors and are at least partially based on design parameters ofthe base station. In addition to large macro cells that provide servicesto numerous devices within relatively large geographical areas, somecellular communication systems are increasingly employing smaller cellsto increase efficiency, improve coverage, improve the quality ofservice, and provide additional services. The smaller cells may includea variety of sizes typically referred to as microcells, picocells andfemtocells. Microcells and picocells are often implemented within officebuildings, shopping centers and urban areas in order to provideadditional security, higher user capacity for the area, additionalservice features, and/or improved quality of service. Femtocells haverelatively smaller geographical areas and are typically implemented atresidences or small office locations. Since typical cellular backhaulresources may not be available in these locations, femtocells aresometimes connected to the cellular infrastructure through DSL or cablemodems. Femtocells are part of the cellular network and, therefore,communicate with the wireless devices using the same techniques as thoseused by macrocells. The proximity of the various base stations andwireless communication devices often results in interference. Inaddition interference of data communications, control channels may alsosuffer performance degradation due to interference.

SUMMARY

A controlling base station sends, to a wireless communication device,control data related to communication between a communication basestation and the wireless communication device. The control data istransmitted in accordance with a communication specification and istransmitted to allow reception by the wireless communication device ofthe control data within a data channel having a frequency and timeallocated by the communication specification for the wirelesscommunication device to receive data transmissions from thecommunication base station.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a communication system in accordance withan exemplary embodiment of the invention.

FIG. 2 is a block diagram of the communication base station connected tothe controlling base station through a core network.

FIG. 3 is a block diagram of the communication base station connected tothe controlling base station through a communication link using X2signaling.

FIG. 4A is an illustration of an exemplary geographical service arearelationship provided by a controlling base station and communicationbase station where the geographic service area of a communication basestation is within a controlling geographic service area of thecontrolling base station.

FIG. 4B is an illustration of an exemplary geographical service arearelationship provided by the controlling base station and thecommunication base station where the geographic service area of acontrolling base station overlaps with the communication geographicservice area of the communication base station.

FIG. 5 is a graphical illustration of transmissions from thecommunication base station and the controlling base station.

FIG. 6 is graphical illustration of the transmissions where thecommunication base station and the controlling base station operate inaccordance with a 3GPP LTE communication specification.

FIG. 7 is an illustration of a sub-frame in accordance with a 3GPP LongTerm Evolution (LTE) communication specification.

FIG. 8 is a transmission timing diagram for exemplary transmissions in acommunication system.

FIG. 9 is a transmission timing diagram for exemplary transmissions in acommunication system where acknowledgments are transmitted within thedata channel.

FIG. 10 is a flow chart of a method performed at the controlling basestation.

FIG. 11 is a flow chart of a method performed at the communication basestation.

FIG. 12 is a flow chart of a method performed at the wirelesscommunication device.

DETAILED DESCRIPTION

FIG. 1 is a block diagram of a communication system 100 in accordancewith an exemplary embodiment of the invention. The communication system100 may be implemented in accordance with any of numerous technologiesand communication standards. For the examples discussed below, thesystem 100 operates in accordance with an orthogonal frequency divisionmultiplex (OFDM) standard. The various functions and operations of theblocks described with reference to the communication system 100 may beimplemented in any number of devices, circuits, and/or elements as wellas with various forms of executable code such as software and firmware.Two or more of the functional blocks of FIG. 1 may be integrated in asingle device and the functions described as performed in any singledevice may be implemented over several devices.

The system 100 includes at least two base stations 102, 104 and awireless communication device 106. In most circumstances, several basestations are connected to a network controller through networkinfrastructure to provide wireless communication services to multiplewireless communication devices. The base stations 102, 104 includewireless transceivers that exchange wireless signals with the wirelesscommunication devices. Transmissions from the base stations and from thewireless communication device are governed by a communicationspecification that defines communication rules and parameters of thetransmission. The communication specification may provide strict rulesfor communication and may also provide general requirements wherespecific implementations may vary while still adhering to thecommunication specification. Although the discussion below is directedto the 3GPP Long Term Evolution (LTE) communication specification, othercommunication specifications may be used in some circumstances. Thecommunication specification defines at least a data channel and acontrol channel for uplink and downlink transmissions and specifies atleast some timing and frequency parameters for a downlink controlchannel from a base station to a wireless communication device. In anOFDM based system, a channel can be defined by allocating specificfrequency-time resources. The granularity of these depends on thespecification and design of the system. Although a particularimplementation may further specify frequency, timing and codingparameters for each base station and/or wireless communication device,conventional systems assume that only the base station transmits controldata within the defined control channel between the base station and thewireless communication device exchanging data with that particular basestation.

In the exemplary embodiments discussed herein, however, the control data108 that represents control information 110 related to the communication112 between a communication base station 102 and the wirelesscommunication device 106 is transmitted by a controlling base station104. The controlling base station 104 transmits the control data 108within the data channel 114 allocated by the communication specificationfor data transmissions from the base stations to the wirelesscommunication devices. Accordingly, the data channel 114 is defined atleast in terms of frequency and time. In conventional systems, thecontrol signals are transmitted by the base stations within a controlchannel defined by the communication specification. Control signals thatare intended for specific wireless communication devices are furthercoded with coding unique to the wireless communication device. Theserial number or device ID, for example, may be used to generate apseudorandom code that is applied to signal that is transmitted withinthe time period and frequency band defined by the control channel. Forthe examples discusses herein, the control signals for controllingcommunication between a wireless communication device and one basestation (communication base station 102) are transmitted by another basestation (controlling base station 104) through a data channel defined bythe communication specification.

The communication 112 between the communication base station 102 and thewireless communication device 106 may be uplink data communication,uplink control communication, downlink data communication, and/ordownlink control information. The control information indicatesparameters related to the communication 112 which allows the wirelesscommunication device 106 to send and receive signals. The parametersinclude timing, frequency, coding and and/or power level information. Ina 3GPP LTE system, for example, the control information 110 indicatesthe subcarrier tones and symbols containing information directed to thewireless communication device 106. In accordance with the exemplaryembodiment, therefore, the wireless communication device 106 receivessignals from the controlling base station 104 containing informationthat allows the wireless communication device 106 to receive data fromthe communication base station 102. The control information may alsoenable transmission of data or uplink control information to thecommunication base station 102. In the exemplary embodiment, the controlinformation 110 conveyed by the control data 108 sent by the controllingbase station 104 is the same or similar to control information 110 thatwould have been transmitted by the communication base station 102 in aconventional system. The control data 108, therefore, represents thecontrol information 110.

The control information 110 is received at the controlling base station104 through a network interface 116. Although some control informationmay be generated by a network controller in some circumstances, thecontrol information 110 is information that the communication basestation 102 should communicate to the wireless communication device 106.Accordingly, the communication base station 112 transmits the controlinformation 110 to the controlling base station 104 which receives thecontrol information 110 through the network interface 116. In somesituations where control information is generated by a networkcontroller, the control information is sent directly from the networkcontroller to the controlling base station 104. In circumstances wherethe controlling base station 104 is allocating resources and has acentral scheduler, the communication base station 102 may send somebasic indications that would assist the controlling base station 104 toformulate the control information for the device 106. As described belowwith reference to FIG. 2 and FIG. 3, the control information 110 may besent directly to the controlling base station 104 through a connectionusing X2 signaling where available or may be sent through a core networkand connections using S1 signaling. In some circumstances, a wirelessbackhaul is used for communication between one or more base stations andthe core network.

The controlling base station 104 generates a downlink transmissionsignal that includes the control data 108 representing the controlinformation 110. In some circumstances, the control information 110 isthe control data 108 although the control data 108 may be derived fromthe control information 110 and is not identical to the controlinformation 110 in other situations. A transmitter 118 in thecontrolling base station 104 transmits the downlink signal including thecontrol data 108 to the wireless communication device 106. The downlinktransmission from the controlling base station 104 includes datadirected to wireless communication devices receiving data from thecontrolling base station 104 and also includes control data 108 forwireless communication devices (such as wireless communication device106) receiving data from other base stations but receiving control datafrom the controlling base station 104 through the data channel.

Accordingly, the controlling base station 104 also provides wirelessservice to other wireless communication devices and, therefore,transmits data and control signals to the wireless communication devicesit is serving as well as transmitting the control data 108 to thewireless communication device through the data channel 114 specified bythe communication specification. Since the wireless communication device106 is within the geographical service area and coverage of thecontrolling base station, the wireless communication device is capableof receiving the control data from the controlling base station.

The communication base station 102 includes circuitry for performing thefunctions described above and which can be described as transmitter 120,receiver 122, and a controller 124. As discussed with reference to FIG.2 and FIG. 3, the communication base station also includes a networkinterface. The controller 124 is any processor, processor arrangement,or computer that can execute code to control devices within thecommunication base station 102 to perform the functions described hereinas well as facilitating the overall functionality of the communicationbase station 102. The receiver 122 is configured to receive wirelesssignals from wireless communication devices and performs demodulation,descrambling, filtering, and other tasks to recover data or controlinformation. In the exemplary embodiment, the receiver operates inaccordance with a 3GPP LTE communication specification. The transmitter120 is configured to transmit wireless signals to wireless communicationdevices and performs modulation, scrambling, filtering, and other tasksto format and transmit data and control information. In the exemplaryembodiment, the transmitter 120 operates in accordance with a 3GPP LTEcommunication specification.

The controlling base station 104 includes circuitry for performing thefunctions described above and which can be described as the networkinterface 116, the transmitter 118 and a controller 126. The controllingbase station 104 also includes a receiver (not shown) in mostcircumstances. The controller 126 is any processor, processorarrangement, or computer that can execute code to control devices withinthe controlling base station 104 to perform the functions describedherein as well as facilitating the overall functionality of thecontrolling base station 104. The transmitter 118 is configured totransmit wireless signals to wireless communication devices and performsmodulation, scrambling, filtering, and other tasks to format andtransmit data and control information. In the exemplary embodiment, thetransmitter 118 operates in accordance with a 3GPP LTE communicationspecification.

The wireless communication device 106 includes circuitry for performingthe functions described above and which can be described as transmitter128, receiver 130, and a controller 132. The controller 132 is anyprocessor, processor arrangement, or computer that can execute code tocontrol devices within the wireless communication device 106 to performthe functions described herein as well as facilitating the overallfunctionality of the wireless communication device 106. The receiver 130is configured to receive wireless signals from base stations andperforms demodulation, descrambling, filtering, and other tasks torecover data or control information. In the exemplary embodiment, thereceiver operates in accordance with a 3GPP LTE communicationspecification. The transmitter 128 is configured to transmit wirelesssignals to base stations and performs modulation, scrambling, filtering,and other tasks to format and transmit data and control information. Inthe exemplary embodiment, the transmitter 128 operates in accordancewith an LTE communication specification.

FIG. 2 is a block diagram of the communication base station 102connected to the controlling base station 104 through a core network202. The communication base station 102 includes a network interface 204that is connected to a communication link 206 that uses S1 signaling toexchange information between the communication base station 102 and thecore network 202. The network interface 116 in the controlling basestation 204 is connected to the core network 202 by a communication link208 that also uses S1 signaling. The network interfaces 116, 204transmit and receive messages in accordance with the S1 signalingprotocol to establish communication between the core network 202 and thebase stations. The communication links 206, 208 may include anycombination of wireless and/or wired backhaul transmission media andequipment.

The core network 202 includes a controller 210 that managescommunications through the core network 202. The controller 210 may beany combination of processors, servers, and other equipment and may begeographically distributed. In some circumstances, the messages betweenthe controlling base station 104 and the communication base station 104are forwarded through the core network 202 with minimal processing bythe controller 210. In other circumstances, the controller 210 mayperform network management functions and may interpret the messages andmake decisions regarding the content of messages sent to the basestations. The level of processing and network management by thecontroller 210 may vary anywhere between simply forwarding messages andfull network management. Accordingly, the control information 110 iseither directly forwarded to the controlling base station from thecommunication base station, slightly modified and forwarded, orinterpreted and processed to generate control information 110 based onthe control information transmitted by the communication base station102.

FIG. 3 is a block diagram of the communication base station 102connected to the controlling base station 104 through a communicationlink 302 using X2 signaling. The network interface 204 is connected tothe communication link 302 that uses X2 signaling to exchangeinformation between the communication base station 102 and thecontrolling base station 104. The communication links 302 may includeany combination of wireless and/or wired backhaul transmission media andequipment. For this example, the control information 110 is directlytransmitted from the communication base station 102 to the controllingbase station 104. The X2 and S1 signaling protocols are defined by the3GPP LTE communication specification protocols. In situations where thecommunication base station is a Femto eNodeB, other backhaul signalingprotocols are used.

FIG. 4A and FIG. 4B are depictions of exemplary geographical servicearea relationships 400, 406 provided by the communication base station102 and the controlling base station 104. The controlling base station104 is capable of providing wireless service to wireless communicationdevices within a control base station geographical service area 402 andthe communication base station 102 is capable of providing wirelessservice to wireless communication devices within a communication basestation geographic service area 404. Accordingly, a geographic servicearea is the coverage area of the base station. The control base stationgeographical service area 402 and the communication base stationgeographic service area 404 may have any of numerous shapes, sizes, andconfigurations. Accordingly, the clouds representing the service areasgenerally illustrate the relationships between the service areas and donot necessarily depict the actual shapes of the service areas. Further,the service areas may contain holes of coverage where service isunavailable. In the interest of clarity and brevity, such features arenot illustrated in the figures. In FIG. 4A, the service area 404 of thecommunication base station 102 is completely within the service area 402provided by the controlling base station 104. Such service arearelationships 400 often occur where some base stations within thecommunication system provide smaller service regions such as microcell,picocell, and femtocell configurations. A femtocell arrangement, forexample, may include a femtocell base station (communication basestation 104) located at a residence where the femtocell is a servicearea for devices used by device users living at the residence. When thewireless communication devices are outside the service area 404, serviceis provided by larger macrocells (e.g. controlling base station 104).When the authorized wireless communication device is at the residence,however, service is provided by the base station presenting the smallerfemtocell service area 404. Accordingly, in most situations, the servicearea 404 of the communication base station 102 will be completely withinthe service area 402 of the controlling base station 104. In somesituations, however the service area 404 may be partially overlappingwith the service area 402 as shown in FIG. 4B.

FIG. 5 is a graphical illustration 500 of transmissions 502, 504 fromthe communication base station 102 and the controlling base station 104.Time-frequency resources are allocated for transmission of communicationdata and control data. A data channel 114 is defined in frequency andtime and a control channel 506 is defined in frequency and time. Thecontrol channel 506 has a frequency band (F) 508 and is allocated atransmission time period (T_(C)) 510. The data channel 114 is allocatedthe frequency band (F) 508 and another time period (T_(D)) 511. For theexample, the frequency band (F) 508 is divided into multiple orthogonalsubcarrier tones in accordance with OFDM techniques. Each channel timeperiod is divided into frames, sub-frames, and symbols in accordancewith the communication specification. The resources are furtherdistributed between the wireless communication devices using coding.Symbols and subcarriers in the data channel 506 are allocated to thewireless communication devices. In some circumstances, some informationmay be provided to the wireless communication device to assist thewireless communication device in locating the control data 108 withinthe control channel 114 intended for the wireless communication device106. Typically, however, the wireless communication device searches thecontrol channel 114 to find the control data 108. In conventionalsystems, each base station transmits control data to the wirelesscommunication devices served by the base station. The control channel ofthe controlling base station and the control channel of thecommunication base station transmission have the same frequency band andtime. The information conveyed in the control channels, however, isdifferent. In the exemplary embodiment, control data 108 associated withthe wireless communication device 106 communicating with thecommunication base station 102 is transmitted by the controlling basestation 104 in the data channel 114. The time-frequency resources usedfor transmitting the control data 108 may be static or dynamic. In otherwords, the location of the control data 108 within the data channel maybe fixed or may change. Further, the location within the channel may hopbetween different portions of data channel. The control data, forexample, may hop across multiple sub-frames of the PDSCH with apredetermined pattern. The wireless communication device 106 may beprogrammed with or may otherwise be made aware of the location of thecontrol data 108 before operation in the system. In other situations,the wireless communication device 106 receives acquisition data from abase station providing the information necessary for the wirelesscommunication device 106 to receive the control data 108. The controldata 108 is coded in accordance with the coding for the intendedwireless communication device 106.

The box with reference number 512 within the communication base stationtransmission 508 is illustrated with dashed lines to show that thecontrol data 108 is not transmitted by the communication base station102 in the exemplary embodiment but would have been transmitted in aconventional system. In some circumstances, the control data 108 may betransmitted by the controlling base station 104 and by the communicationbase station 102, although such an implementation may add interferenceand complexity in the system. In the exemplary embodiment thecommunication base station 102 refrains from transmitting any controlinformation where control data 108 is transmitted by the controllingbase station 104. Further, the communication base station 102 refrainsfrom transmitting any signals within the control channel 506 insituations where a controlling base station 104 transmits control data108. In addition, the communication base station 102 refrains fromtransmitting any signals within the time-frequency resources used by thecontrolling base station to transmit the control data 108. Such anarrangement minimizes interference and noise in situations where thewireless communication device is within the control base stationgeographic service area 402 and the communication base stationgeographical service area 404.

The transmission continues in time as illustrated by the dashed lines ofthe second transmissions of the control channel and the three dots inFIG. 5. The transmissions may include other channels and sub-channelsnot shown in FIG. 5. For example, broadcast messages, pilot signals, andsynchronizing channels may be used.

Therefore, the communication system 100 includes a communication basestation and a controlling base station where the controlling basestation sends control data over a data channel to a wirelesscommunication device communicating with the communication base station.The communication base station has a communication base stationgeographic service area and is configured to transmit data to thewireless communication device within the service area through a portionof a data channel. The controlling base station has a control basestation geographical service area larger than the communication basestation geographic service area. The controlling base station isconfigured to transmit control data to the wireless communication devicethrough another portion of the data channel where the control datarepresents control information related to communication between thewireless communication device and the communication base station. In theexemplary embodiments, the power levels and timing of signals receivedat the wireless communication device 106 are closely monitored and thepower levels and timing of the signals transmitted by the controllingbase station in the data channel to the wireless communication device106 are adjusted in accordingly.

FIG. 6 is graphical illustration 600 of the transmissions 502, 504 wherethe communication base station and the controlling base station operatein accordance with a 3GPP LTE communication specification. For theexample of FIG. 6, the controlling base station 104 is an eNodeB with ageographical service area greater than geographical service area of aneNodeB that is operating as the communication base station. Accordingly,a larger service area (LSA) eNodeB, such a macro eNodeB has a largerservice area than a smaller service area (SSA) eNodeB such as a MicroeNodeB, Pico eNodeB, or Femto eNodeB.

For the example of FIG. 6, the controlling base station transmission 502is the larger service area eNodeB transmission (LSA transmission) andthe communication base station transmission 504 is the smaller servicearea eNodeB transmission (SSA transmission) where the transmissions areformatted and transmitted in accordance with the 3GPP LTE communicationspecification. Therefore, the control channel 502 is a Physical DownlinkControl Channel (PDCCH) 602 and the data channel 114 is a PhysicalDownlink Shared Channel (PDSCH) 604 for this example. The control data108 is transmitted in the LSA transmission 502 within the PDSCH 604. Thecontrol data 108 is coded in accordance with the wireless communicationdevice identification and the LSA eNodeB and is transmitted over symbols606 and subcarriers 608 of the PDSCH 604. The time-frequency resources611 in the PDSCH 604 in the SSA transmission 504 that correspond tosubcarriers 608 and time 606 used to transmit the control data in thePDSCH of the LSA transmission 502 are not used for any data. Therefore,the SSA eNodeB refrains from transmitting within time-frequencyresources 611 of the PDSCH 604. Accordingly, the controlling basestation transmits the control data in a portion of the data channelduring a time when the communication base station is not transmitting inthe portion of the data channel. The communication base stationtherefore, refrains from transmitting any signals within thetime-frequency resources used by the controlling base station fortransmitting the control data. Further, the SSA eNodeB refrains fromtransmitting in the PDCCH 602.

For this example, communication acquisition information 614 istransmitted within the broadcast channel 616. The communicationacquisition information 614 includes all additional information requiredfor a wireless communication device 106 entering the service area toconfigure its receiver to receive and decipher transmitted control data.Accordingly, the communication acquisition information 614 includes thescrambling code of the eNodeB transmitting the control channel andtiming information if needed, for example.

In the exemplary embodiment, the communication acquisition information614 in the broadcast channel within the SSA eNodeB transmission(communication base station transmission 504) indicates that the LSAeNodeB will be transmitting the control data 108 to the wirelesscommunication device 106. The communication acquisition information 614includes the information that allows the wireless communication deviceto receive the control data 108 from the LSA eNodeB (controlling basestation 104). In this embodiment, the broadcast channel 616 is aBroadcast Channel (BCH) transmitted over the Physical Broadcast Chanel(PBCH) 618 in accordance with the 3GPP LTE communication specification.

The broadcast channel includes an indicator 620, such a one bit flag,indicating to the user equipment (UE) (wireless communication device106) that the LSA eNodeB will be transmitting the control data 108. Insome circumstances the indicator 620 may be omitted.

FIG. 7 is an illustration of a sub-frame 700 in accordance with a 3GPPLTE communication standard. The sub-frame 700 includes two slots 702,704, where each slot includes seven symbol times 706. The symbol times0, 1 and 2 in the first slot 702 form the PDCCH 602. Pilot signals 708are injected at symbol times 0 and 4. The broadcast channel is the PBCHspans portions of symbols time 3 and 4 of the first slot 702 andportions of symbol time 0 and 1 of the second slot 704. The PDSCH 604includes is covered by the remainder of symbol times 3-6 of the firstslot 702 and symbol times 1-6 of the second slot 704. The sub-frame 700also includes a primary synchronization channel (P-SCH) 710 and asecondary synchronization channel (S-SCH) 712.

FIG. 8 is a transmission timing diagram for exemplary transmissions in acommunication system 100. The timing diagrams of FIG. 8 and FIG. 9represent only examples of transmission timings. Other scenarios arepossible. For example, transmissions 802 and 804 may be simultaneous insome circumstances. For the example of FIG. 8, the communication basestation 102 is a Pico eNodeB and the controlling base station is a MacroeNodeB where the geographical service area of the Pico eNodeB is withinthe geographical service area of the Macro eNodeB. Transmissions mayoccur in the system 100 that are not reflected in transmission timingdiagram of FIG. 8.

During transmission 802, the Pico eNodeB transmits communicationacquisition information 620 over the P-SCH, S-SCH, and PBCH to the UE(wireless communication device 106) that will receive data from the PicoeNodeB. After synchronization with the pico eNodeB using P-SCH and S-SCHchannels, the PBCH is received. The communication acquisitioninformation 620 in the PBCH provides information to the UE to allow theUE to receive the control data 108 from the Macro eNodeB.

During transmission 804, the Pico eNodeB sends the control information110 to the Macro eNodeB. As discussed above, the control information 110may sent over X2 signaling connection where available or through a corenetwork using S1 signaling.

During transmission 806, the Macro eNodeB transmits the control data 108over the PDSCH 604 to the UE. The control data 108 provides the UE withthe control information necessary to communicate with the Pico eNodeB.In this example, the Pico eNodeB does not transmit its own PDCCH (thechannel remains blank).

During transmission 808, the Pico eNodeB transmits communication data tothe UE over the PDSCH.

During transmission 810, the UE transmits a transmission that maycontain communication data control data to the Pico eNodeB.

During transmission 812, the Pico eNodeB transmits an acknowledgment(ACK) information to the Macro eNodeB. The acknowledgment informationmay be negative acknowledgment (NACK) in some circumstances. The ACKprovides feedback regarding whether a communication sent by the UE wassuccessfully received.

During transmission 814, the Macro eNodeB sends an ACK message over thePHICH that corresponds to the ACK information received from the PicoeNodeB. In this example, therefore, the ACK is first sent to the MacroeNodeB over a S1 or X2 connection and forwarded by the Macro eNodeB tothe UE. The PHICH is transmitted over the PDCCH or over a separatechannel within PDSCH region.

Due to delays in the backhaul and processing, transmissions 816 to andfrom the UE may occur before the PHICH is sent from the Macro eNodeB.The UE includes sufficient memory to buffer communication so that if atransmission is not successfully received at the Pico eNodeB, the UE canretrieve the appropriate data for retransmission. Accordingly, a largerbuffer may be used in the system as compared to conventional systemswhere the ACK is received from the Pico eNodeB.

FIG. 9 is a transmission timing diagram for exemplary transmissions in acommunication system 100 where acknowledgments are transmitted withinthe data channel. For the example of FIG. 9, the communication basestation 102 is a Pico eNodeB and the controlling base station is a MacroeNodeB where the geographical service area of the Pico eNodeB is withinthe geographical service area of the Macro eNodeB. Transmissions mayoccur in the system 100 that are not reflected in transmission timingdiagram of FIG. 8. Transmissions 802-810 are performed as describedabove with reference to FIG. 8.

During transmission 902, the Pico eNodeB transmits the ACK to the UEover the PDSCH. Therefore, instead of sending the acknowledgment to theMacro eNodeB for transmission to the UE in the PHICH channel, the PicoeNodeB transmits the acknowledgment directly to the UE using the datachannel (PDSCH).

FIG. 10 is a flow chart of a method performed at the controlling basestation 104. Although the method may be performed using any combinationof code and/or hardware, the method is formed by executing code on thecontroller 126 within the controlling base station 104 in the exemplaryembodiment.

At step 1002, the control information 110 is received. The controlinformation 110 is received through the network interface 116 whereinthe network interface 116 may be connected to a core network 202 or tothe communication base station 102. The control information 110 includesinformation related to the communication between the communication basestation 102 and the wireless communication device 106 and, when receivedat the wireless communication device 106, enables the wirelesscommunication device 106 to communicate with the communication basestation 102. Where the controlling base station is connected to the corenetwork 202, the control information 110 may be received over aconnection 208 using S1 signaling. Where the controlling base station104 is connected to the communication base station 104, the controlinformation 110 may be received over a connection 302 using X2signaling.

At step 1004, the control data 108 based on the control information 110is transmitted to the wireless communication device 106. Usingcommunication acquisition information that is transmitted by thecommunication base station over the broadcast channel, the transmitter118 in the controlling base station 104 transmits the control datawithin the data channel 114. In some circumstances, the controlling basestation transmits the control data in a portion of the data channelduring a time that the communication base station is not transmittingany signals in that portion. The communication base station therefore,refrains from transmitting any signals within the time-frequencyresources used by the controlling base station for transmitting thecontrol data.

At step 1006, acknowledgment information is received from thecommunication base station.

At step 1008, an acknowledgment message based on the acknowledgmentinformation is transmitted to the wireless communication device 106. Thetransmitter transmits the acknowledgment message through the PHICHchannel where the system operates in accordance with a 3GPP LTEspecification. Steps 1006 and 1008 are omitted in implementations wherethe communication base station 102 transmits the acknowledgment messageover the data channel.

FIG. 11 is a flow chart of a method performed at the communication basestation 102. Although the method may be performed using any combinationof code and/or hardware, the method is formed by executing code on thecontroller 124 within the communication base station 102 in theexemplary embodiment.

At step 1102, the control information 110 is transmitted to thecontrolling base station 104. The control information 110 is transmittedthrough the network interface 204 where the network interface 204 may beconnected to a core network 202 or to the controlling base station 104.The control information 110 includes information related to thecommunication between the communication base station 102 and thewireless communication device 106 and, when received at the wirelesscommunication device 106, enables the wireless communication device 106to communicate with the communication base station 102. Where thecommunication base station 102 is connected to the core network 202, thecontrol information 110 may be transmitted over a connection 206 usingS1 signaling. Where the communication base station 102 is connected tothe controlling base station 104, the control information 110 may betransmitted over a connection 302 using X2 signaling.

At step 1104, communication data is transmitted in accordance with thecontrol information. The communication data is transmitted over the datachannel.

At step 1106, an uplink transmission is received from the wirelesscommunication device 106.

At step 1108, an acknowledgment message is transmitted to the wirelesscommunication device over the data channel. The acknowledgment messageindicates successful reception of the uplink transmission.Alternatively, the communication base station can transmit theacknowledgment information to the controlling base station 104 fortransmission as an acknowledgment message in the PHICH.

FIG. 12 is a flow chart of a method performed at the wirelesscommunication device 106. Although the method may be performed using anycombination of code and/or hardware, the method is formed by executingcode on the controller 132 within the wireless communication device 106in the exemplary embodiment.

At step 1202, communication acquisition information is received from thecommunication base station 102 through the broadcast channel.

A step 1204, control data 108 is received from the controlling basestation 104 through the data channel 114. The receiver 130 is configuredin accordance with the communication acquisition information to enablethe wireless communication device 106 to receive the control data. Thecontrol data 108 represents the control information 110 which includesinformation related to the communication between the communication basestation 102 and the wireless communication device 106 and, when receivedat the wireless communication device 106, enables the wirelesscommunication device 106 to communicate with the communication basestation 102.

At step 1206, communication data is received from the communication basestation 102. Using the control data 108 received from the controllingbase station 104, the receiver 130 is configured to receivecommunications from the communication base station 102.

At step 1208, the wireless communication device 106 transmits an uplinktransmission to the communication base station 102. Using the controldata 108 received from the controlling base station 104, the transmitter128 is configured to transmit uplink communications to the communicationbase station 102.

At step 1208, an acknowledgment message is received at the wirelesscommunication device. In situations where the communication base station102 sends the acknowledgment message, the acknowledgment message isreceived over the data channel. In situations where the controlling basestation sends the acknowledgment message, the acknowledgment message isreceived over the PHICH channel.

Therefore, the control data transmission management discussed aboveprovides that a base station with a large coverage area transmit thecontrol information for base stations having smaller coverage areaswithin the larger coverage area. Control channels are designed to berobust by having lower rate coding, higher power, and other parameterswhich allow the wireless communication devices to more easily receiveand decode the control information. As a result, wireless communicationdevices communicating with the smaller area base stations can, in mostcircumstances, easily receive the control signals from the larger areabase stations while communicating with the smaller area base stations.The control data transmission management discussed herein, therefore,takes advantage of the robustness of the high power of the larger areabase stations and reduces interface by allowing the small area basestations to refrain from transmitting control signals. The system can befurther optimized by allocating frequencies to particular base stationsand wireless communication devices under certain scenarios. Someexamples where the control management techniques may used to minimizeinterference include situations where a Pico eNodeB is transmitting tousers in a building and a macro eNodeB is transmitting to users outsidethe building. By transmitting control signals from the macro eNodeB tothe users in the building instead of from the Pico eNodeB, the PicoeNodeB does not cause interface with users outside the building usingthe macro eNodeB. Other interference scenarios and techniques forbroadcasting overhead parameters that may be coupled with the teachingsherein are presented in US Patent Publication US 2008/0279168, publishedNov. 13, 2008, Ser. No. 11/746,501, and entitled “SYSTEM AND METHOD FORBROADCASTING OVERHEAD PARAMETERS IN POOR COVERAGE REGIONS”, which isincorporated by reference in its entirety, herein.

Clearly, other embodiments and modifications of this invention willoccur readily to those of ordinary skill in the art in view of theseteachings. The above description is illustrative and not restrictive.This invention is to be limited only by the following claims, whichinclude all such embodiments and modifications when viewed inconjunction with the above specification and accompanying drawings. Thescope of the invention should, therefore, be determined not withreference to the above description, but instead should be determinedwith reference to the appended claims along with their full scope ofequivalents.

What is claimed is:
 1. A base station comprising: a controllerconfigured to control a first communication link with a user equipmentand maintain the first communication link while the user equipment has asecond communication link with another base station; a receiverconfigured to receive control information from the another base stationon X2 or S1 interface, wherein the control information at least includesinformation indicating radio resources of the another base stationassociated with the second communication link; and a transmitterconfigured to transmit control data to the user equipment on a datachannel associated with the second communication link, wherein thecontrol data is, at least partially, based on the control information.2. A method for a base station, the method comprising: controlling afirst communication link with a user equipment; receiving controlinformation from another base station on X2 or S1 interface, wherein thecontrol information at least includes information indicating radioresources of the another base station associated with a secondcommunication link between the user equipment and the another basestation; transmitting control data to the user equipment on a datachannel associated with the second communication link, wherein thecontrol data is, at least partially, based on the control information;and maintaining the first communication link while the user equipmenthas the second communication link with the another base station.
 3. Auser equipment comprising: a controller configured to control a firstcommunication link with a first base station; and a receiver configuredto receive control data from the first base station on a data channelassociated with a second communication link between the user equipmentand a second base station, wherein the control data is partially basedon control information; wherein the controller is further configured tomaintain the first communication link while the user equipment has thesecond communication link, and the control information is transmittedfrom the second base station to the first base station on X2 or S1interface, and the control information at least includes informationindicating radio resources of the second base station associated withthe second communication link.
 4. An apparatus for wirelesscommunication, comprising: a processor; memory in electroniccommunication with the processor; wherein the processor is configuredto: control a first communication link with a first base station;receive control data from the first base station on a data channelassociated with a second communication link between the user equipmentand a second base station, wherein the control data is partially basedon control information; wherein the processor is further configured tomaintain the first communication link while the user equipment has thesecond communication link, and the control information is transmittedfrom the second base station to the first base station on X2 or S1interface, and the control information at least includes informationindicating radio resources of the second base station associated withthe second communication link.